Spring-Loaded Sod Cutter For Vibratory Plow

ABSTRACT

A sod cutting blade pivotally supported on a plow assembly frame such that the sod cutting blade is able to pivot and pass over an obstruction when encountered during a plowing operation. The plow assembly has a spring that is used to bias the sod cutter into the ground.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional patent applicationSer. No. 61/770,024, filed on Feb. 27, 2013, the entire contents ofwhich are incorporated herein by reference.

FIELD

The present invention relates generally to the field of utilityinstallation and in particular to the use of plows for the installationof underground utilities.

SUMMARY

The present invention is directed to a system for installing a utilityunderground. The system comprises a mobile power source comprising awork machine frame and a plow assembly connected to the power source.The plow assembly comprises an arm pivotally connected to the workmachine frame at a first end of the arm, a shaker box connected to asecond end of the arm, a plow blade connected to the shaker box, and apivotal sod cutting member supported by the arm between the first end ofthe arm and the second end of the arm ahead of the plow blade. The sodcutting member has a cutting length less than a length of the plow bladeand pivots when the sod cutting member engages an undergroundobstruction. A biasing member is connected to the sod cutting member andthe arm to bias the sod cutting member into the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a vibratory plow and sodcutter.

FIG. 2 is a diagrammatic representation of a sod cutter of the presentinvention.

FIG. 3 is a diagrammatic representation of an alternative sod cutter ofthe present invention.

DESCRIPTION

FIG. 1 illustrates a vibratory plow machine 10 used for the installationof slender underground utilities (cables, small pipes, etc.). Thesemachines typically have a power unit 14 on wheels 16 or tracks (notshown) for moving the unit. The power unit 14 pulls a plow unit 18 thathas a vibratory shaker box 20 and plow blade 22. The vibratory shakerbox 20 will typically feature a set of internal rotating eccentricweights (not shown) that cause a vibratory motion of the shaker box asthe weights are rapidly rotated. The shaker box 20 connects to the plowblade 22 extending into the soil 24 which creates a narrow slot in theground as the machine 14 advances forward. Typically, the utilityservice is fed into the narrow slot in the ground right behind the plowblade 22.

In many instances, this type of machine is used to install services innicely landscaped areas with established turf. In these instances, thevibratory plow machines 10 commonly run a sod cutter 26 in front of theplow blade 22 to pre-cut the sod 28 in front of the plow blade tominimize the turf damage done as the vibratory plow machine operates.The sod cutter 26 provides a clean cut in Bermuda grass or similargrasses with rhizomes, or “runners” that spread out on the surface ofthe ground and helps to prevent a pulling and uprooting of the grass asthe blade passes. Sod cutter types that have been used include a narrowfixed blade or a rolling disc to cut the sod.

One problem that can be encountered with the current sod cutters is whenan obstacle 30 such as a stone or tree root exists at or close to thesurface of the ground. This type of obstacle can damage the sod cutter26, and/or cause the shaker box 20 to be lifted up as the sod cutterpasses over the obstacle, resulting in an inconsistent burial depth forthe installed utility.

Turning to FIG. 2, the sod cutter 32 of the present invention is shownmounted on the lower arm 34 of a vibrator plow assembly 18. The sodcutter 32 is pinned in place at the pinned pivot location 36 instead ofthe rolling disc shown in FIG. 1.

In use, the device functions as follows. The sod cutter 32 extends intothe surface of the ground 28 (typically about 3″-6″) and cuts the sod infront of plow blade 22. Springs 38 are attached to a device frame 40 andto an attachment point 42 above the pinned pivot 36 on the blade 32. Inthis configuration, the spring 38 provides a measure of preload on theblade 32 to keep it from freely pivoting and moving backward. Thepreload on the blade 32 is sufficient to allow the blade to cut throughnormal sod and vegetation as is found in an established lawn withoutpivoting backward. When an obstacle of sufficient size, such as a largestone or tree root is encountered, the preload on the blade 32 isovercome and the blade may pivot back allowing the sod cutter to passover the obstacle without damage and without causing the shaker box tobe lifted up relative to the ground surface. After passing over theobstacle 30 (FIG. 1), the preload of the spring(s) 38 on the bladecauses the sod cutter blade 32 to once again extend into the surface ofthe ground and continue cutting the vegetation as the machine 14 isadvanced forward.

Continuing with FIG. 2, a generalized form of the spring-loaded sodcutter for a vibratory plow is shown. The version illustrated in FIG. 2is shown on a frame 40 which may be added or removed from the vibratoryplow assembly 18. Alternatively, the spring loaded sod cutter 32 can bean integral part of the plow assembly 18. The sod cutter would bemounted on the lower arm 34 of the vibratory plow attachment 18. The sodcutter 32 is free to pivot about its attachment point 36 as illustratedin FIG. 2. A mechanical stop (not shown) may be used to limit the amountof forward rotation of the sod cutter in order to maintain pre-load onthe spring 38 used to bias the sod cutter. Spring 38 may be a tensionspring The spring may be made from steel. Alternatively, the spring 38could be an elastomer like rubber or urethane, or a gas filled spring.By altering the geometry slightly, a compression spring made of steel,elastomer, or of a gas-charged design could be used to maintain preloadon the blade 32. Alternatively, a torsion spring could be adapted toprovide the necessary preload to hold the sod cutter in its forwardposition when an obstacle is not encountered.

The leading edge 44 of the sod cutter 32 will have a semi-sharpenedleading edge comparable to a knife blade, and the toe 46, or leadingpoint, of the sod cutter will extend forward of the pivot point 36 asshown in FIG. 2.

FIG. 3 illustrates an alternative embodiment of the spring-loaded sodcutter. In this embodiment, a rolling disk 26, “pizza-cutter” style sodcutter illustrated in FIG. 1 is utilized. However, instead of a fixedmounting as shown in FIG. 1, the rolling disk cutter 26 is mounted on anarm 46 which may pivot to allow the sod cutter 26 to float up out of theway of an obstacle 30 (FIG. 1). As illustrated in FIG. 3, a compressionspring 48 is used to maintain a preload on the pivoting arm 46 to holdthe rolling disk cutter 26 in the ground 28 when an obstacle 30 (FIG. 1)is not encountered. The spring 48 could be made of steel, and elastomer,or of a gas-charged design. It will be appreciated that by altering thegeometry of the arm 46 and pivot point 50 slightly, a tension spring ora torsion spring could be used to maintain the preload on this style ofcutter.

The present invention is also directed to a method of using the abovedescribed devices to cut a trench in the Earth and install a utility.

Various modifications can be made in the design and operation of thepresent invention without departing from the spirit thereof Thus, whilethe principal preferred construction and modes of operation of theinvention have been explained in what is now considered to represent itsbest embodiments, which have been illustrated and described, it shouldbe understood that the invention may be practiced otherwise than asspecifically illustrated and described.

What is claimed is:
 1. A system for installing a utility underground,the system comprising: a mobile power source comprising a work machineframe; a plow assembly connected to the power source, the plow assemblycomprising: an arm pivotally connected to the work machine frame at afirst end of the arm; a shaker box connected to a second end of the arm;a plow blade connected to the shaker box; a pivotal sod cutting membersupported by the arm between the first end of the arm and the second endof the arm ahead of the plow blade, wherein the sod cutting member has acutting length less than a length of the plow blade and pivots when thesod cutting member engages an underground obstruction; and a biasingmember connected to the sod cutting member and the arm to bias the sodcutting member into a ground surface.